The present invention relates to an improvement in an apparatus and method for distributing and casting a lining material onto the whole inner surface of a molten metal vessel during the application of an indeterminately shaped or amorphous refractory material to the inner surface of molten metal vessels.
In accordance with the invention, the term molten metal vessel means a vessel having a circular or elliptical cross-sectional shape such as a ladle or vacuum degassing vessel used in the making of steel.
Recently, a so-called cast lining method has been used for lining such a vessel with an amorphous refractory, in which a lining frame (or a core) is placed at a predetermined position within the vessel and an amorphous refractory is cast into the space between the lining frame and a permanent lining refractory previously installed in the vessel, thereby applying an inner lining to the vessel.
At the early stage, a lining method was developed comprising adding a small quantity, e.g., 5 to 7% of mixing water to an amorphous refractory, converting the same into a high-density slurry by vibration mixing, conveying the slurry as such to a large vessel and casting the slurry into the vessel while vibrating it thereby filling the vessel with the refractory. This method had the disadvantage of requiring several high-frequency vibrators with the accompanying necessity for noise suppressing measures and also requiring a variety of special large devices for providing the necessary vibrations during the transportation of the refractory, for vibrating the large vessel, etc., thus making the method unpractical.
Another casting method was designed so that a cylindrical lining frame (or a core) was arranged within a ladle placed on a suitable ground and a castable refractory having a water content of 7 to 8% was casted, while mixing by a mixer, through a trough directly into the space between the outer wall of the lining frame and the permanent lining refractory previously installed on the inner surface of the ladle. With this method, the falling place of the castable refractory was confined to the limited portion of the surrounding area of the ladle where the mixer was positioned, with the result that the refractory was piled in the limited portion and this piled refractory not only tended to move the frame under its pressure but also required the operation of levelling the piled refractory in the circumferential direction of the ladle by hand. Thus, there was the disadvantage of causing circumferential variations in the quality of the installed lining, thus causing an unbalanced melting loss during the use of the ladle and thereby reducing the service life of the ladle.
In an attempt to overcome the foregoing deficiencies, a method was devised in which a conical distributor was installed on the top of a ladle so that a castable refractory mixed by a mixer was distributed from the top of the distributor by means of a trough or belt conveyor to fall along the inclined surface of the conical distributor and simultaneously the ladle was vertically and laterally oscillated and/or rotated on an oscillatory rotating table, thereby casting the refractory. A disadvantage of this method was that while the distributor was conical in shape, the casting material was simply dropped from one place of the distributor top with the result that it was difficult to uniformly scatter the casting material in the circumferential direction of the ladle and therefore it was necessary to install a large equipment such as an oscillatory rotating table for oscillating and rotating the ladle which was as heavy as about 200 tons. Another disadvantage was that there was a limit to the mixer capacity (usually about 2 tons) and therefore it was necessary to perform the lining operation while intermittently repeating the mixing operation, thus making it impossible to effect a continuous casting operation and deteriorating the efficiency. Still other disadvantages were the occurence of dust in the vicinity of the mixer, the need to dispose the waste water due to the washing of the interior of the mixer and other defects from the operating environmental point of view.
To overcome these deficiencies, another method of continuously casting an amorphous refractory was devised, the method comprising mixing an amorphous refractory by a mixer located remote from a ladle, placing the refractory in an intermediate bucket, moving the intermediate bucket by a transfer crane to a position above a conical distributor arranged on the ladle and placing the bucket on the distributor and simultaneously opening the gate in the lower part of the intermediate bucket thereby causing the amorphous refractory to fall. This method was disadvantageous in that the conveyance of mixed refractory from the mixer to the ladle had to be repeated frequently making the use of this method impossible in cases where the operating rate of the existing cranes had nothing in reserve and also there was the need to provide additional conveyance equipment for conveying the bucket exclusively.
On the other hand, an apparatus was proposed in which with a main object of distributing a refractory material along the entire inner surface of a ladle uniformly, a rotary chute was arranged below the forward end of a belt conveyor for conveying the mixed refractory from a mixer and the rotary chute discharge end was rotated along the gap surrounding a lining frame within the ladle. This apparatus was disadvantageous in that the apparatus was not only complicated and large in mechanical construction but also the rotation of the rotary chute just above the ladle presented a problem from the standpoint of safety to operators in cases where any operation had to be performed inside or on the ladle.
As described hereinabove, the prior art lining apparatus and methods are all disadvantageous in that the lining material cannot be distributed uniformly within a ladle and the lining life is short, that much labor is required, that the continuous operation is not easy, that much funds are required for the necessary equipment, that there are difficulties from the environmental and safety points of view and so on.